Package structure and method of forming the same

ABSTRACT

A package structure includes a first dielectric layer, a first semiconductor device over the first dielectric layer, a first redistribution line in the first dielectric layer, a second dielectric layer over the first semiconductor device, a second semiconductor device over the second dielectric layer, a second redistribution line in the second dielectric layer, a conductive through-via over the first dielectric layer and electrically connected to the first redistribution line, a conductive ball over the conductive through-via and electrically connected to the second redistribution line, and a molding material. The molding material surrounds the first semiconductor device, the conductive through-via, and the conductive ball, wherein a top of the conductive ball is higher than a top of the molding material.

PRIORITY CLAIM AND CROSS-REFERENCE

This present application is a continuation application of U.S. patentapplication Ser. No. 15/800,035, filed Oct. 31, 2017, now U.S. Pat. No.10,784,220, issued Sep. 22, 2020, which claims priority to U.S.Provisional Application Ser. No. 62/479,237, filed Mar. 30, 2017, all ofwhich are herein incorporated by reference in their entirety.

BACKGROUND

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. These smallerelectronic components also require smaller packages that utilize lessarea than packages of the past, in some applications. Some smaller typesof packaging for semiconductors include quad flat pack (QFP), pin gridarray (PGA), ball grid array (BGA), flip chips (FC), three dimensionalintegrated circuits (3DICs), wafer level packages (WLPs), bond-on-trace(BOT) packages, and package on package (PoP) structures.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1-19 are cross-sectional views of intermediate stages in themanufacturing of a package structure in accordance with some embodimentsof the present disclosure;

FIG. 20 is a cross-sectional view of a semiconductor assembly inaccordance with some embodiments of the present disclosure;

FIGS. 21-22 are cross-sectional views of intermediate stages in themanufacturing of the package structure after the step of FIG. 17;

FIG. 23 is a cross-sectional view of a package structure in accordancewith some embodiments of the present disclosure;

FIGS. 24-32 are cross-sectional views of intermediate stages in themanufacturing of a package structure in accordance with some embodimentsof the present disclosure;

FIG. 33 is a cross-sectional view of a molded package in accordance withsome embodiments of the present disclosure;

FIG. 34 is a cross-sectional view of a molded package in accordance withsome embodiments of the present disclosure;

FIG. 35 is a cross-sectional view of a package structure in accordancewith some embodiments of the present disclosure;

FIGS. 36-51 are cross-sectional views of intermediate stages in themanufacturing of a package structure in accordance with some embodimentsof the present disclosure;

FIG. 52 is a cross-sectional view of a TIV package in accordance withsome embodiments of the present disclosure;

FIG. 53 is a cross-sectional view of a TIV package in accordance withsome embodiments of the present disclosure; and

FIG. 54 is a cross-sectional view of a package structure in accordancewith some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Other features and processes may also be included. For example, testingstructures may be included to aid in the verification testing of the 3Dpackaging or 3DIC devices. The testing structures may include, forexample, test pads formed in a redistribution layer or on a substratethat allows the testing of the 3D packaging or 3DIC, the use of probesand/or probe cards, and the like. The verification testing may beperformed on intermediate structures as well as the final structure.Additionally, the structures and methods disclosed herein may be used inconjunction with testing methodologies that incorporate intermediateverification of known good dies to increase the yield and decreasecosts.

FIGS. 1-19 are cross-sectional views of intermediate stages in themanufacturing of a package structure in accordance with some embodimentsof the present disclosure. Reference is made to FIG. 1. An adhesivelayer A1 is formed on a carrier C1. The carrier C1 may be a blank glasscarrier, a blank ceramic carrier, a metal frame, or the like. Theadhesive layer A1 may be made of an adhesive, such as ultra-violet (UV)glue, light-to-heat conversion (LTHC) glue, or the like, although othertypes of adhesives may be used. A buffer layer 110 is formed over theadhesive layer A1 using a spin coating process, a film laminationprocess, or a deposition process, as examples. The buffer layer 110 is adielectric layer which may be a polymer layer. The polymer layer mayinclude, for example, polyimide, polybenzoxazole (PBO), benzocyclobutene(BCB), an ajinomoto buildup film (ABF), a solder resist film (SR), orthe like. In some embodiments, the buffer layer 110 may be a compositelayer that combines the buffer layer 110 with the adhesive layer A1 intoone layer. The buffer layer 110 may be a substantially planar layerhaving a substantially uniform thickness, in which the thickness may begreater than about 2 μm or may be in a range from about 0.5 μm to about40 μm. In some embodiments, top and bottom surfaces of the buffer layer110 are also substantially planar.

Reference is made to FIG. 2. A dielectric layer 120 is formed over thebuffer layer 110 using a spin coating process or a lamination process,as examples. Thereafter, the dielectric layer 120 is patterned to formopenings O1. The openings O1 may be arranged in a grid pattern of rowsand columns that corresponds to a subsequently formed ball grid array(BGA). The dielectric layer 120 may be patterned using a lithographyprocess. In some embodiments, the dielectric layer 120 may be a polymerlayer. The polymer layer may include, for example, polyimide,polybenzoxazole (PBO), benzocyclobutene (BCB), an ajinomoto buildup film(ABF), a solder resist film (SR), or the like.

Reference is made to FIG. 3. A seed layer 132 is formed over the carrierC1. The seed layer 132 is formed over the buffer layer 110 and thedielectric layer 120 on the carrier C1. The seed layer 132 includes, forexample, titanium (Ti), copper (Cu), or a combination thereof and isdeposited using physical vapor deposition (PVD) or by lamination of afoil material in some embodiments, for example. Alternatively, the seedlayer 132 may include other materials and dimensions and may be formedusing other methods. Thereafter, a photoresist P1 is applied over theseed layer 132 and is then patterned. As a result, openings O2 areformed in the photoresist P1 through which some portions of the seedlayer 132 are exposed.

Reference is made to FIG. 4. Conductors 134 are respectively formed inthe openings O2 of the photoresist P1 through plating which may beelectro plating or electro-less plating. The conductors 134 are platedon the exposed portions of the seed layer 132. The conductors 134 mayinclude a metal or a metal alloy including aluminum, copper, tungsten,and/or alloys thereof. After the plating of the conductors 134, thephotoresist P1 is removed to expose some portions of the seed layer 132.

Reference is made to FIG. 5. An etch operation is performed to removethe exposed portions of the seed layer 132, and the etch operation mayinclude an anisotropic etching. Some portions of the seed layer 132 thatare covered by the conductors 134, on the other hand, remain not etched.Throughout the description, the conductors 134 and the remainingunderlying portions of the seed layer 132 are in combination referred toas redistribution lines (RDLs) 130. Although the seed layer 132 is shownas a layer separate from the conductors 134, when the seed layer 132 ismade of a material similar to or substantially the same as therespective overlying conductors 134, the seed layer 132 may be mergedwith the conductors 134 with no distinguishable interface therebetween.In alternative embodiments, there exist distinguishable interfacesbetween the seed layer 132 and the overlying conductors 134.

Reference is made to FIG. 6. A dielectric layer 140 is formed over theRDLs 130. The dielectric layer 140 may include a polymer, such aspolyimide, benzocyclobutene (BCB), polybenzoxazole (PBO), or the like,which is deposited using a spin coating process or a lamination process,as examples. Alternatively, the dielectric layer 140 may includenon-organic dielectric materials, such as silicon oxide, siliconnitride, silicon carbide, silicon oxynitride, or the like. Thedielectric layer 140 is patterned using a lithography process. Forexample, a photoresist (not shown) may be formed over the dielectriclayer 140, and the photoresist is patterned by exposure to energy orlight reflect from or transmitted through a lithography mask having apredetermined pattern thereon. The photoresist is developed, and exposed(or unexposed, depending on whether the photoresist is positive ornegative) regions of the photoresist are removed using an ashing and/oretching process. The photoresist is then used as an etch mask during anetch process. Exposed portions of the dielectric layer 140 are removedduring the etch process to form openings O3, through which some portionsof the RDLs 130 are exposed. Afterwards, the photoresist is removed.

Reference is made to FIG. 7. A seed layer 152 is formed over the carrierC 1. The seed layer 152 is formed over the dielectric layer 140 and inthe openings O3 (shown in FIG. 6) of the dielectric layer 140. In someembodiments, the seed layer 152 is conformally formed on the dielectriclayer 140 and in the openings O3 (shown in FIG. 6). The seed layer 152includes, for example, titanium (Ti), copper (Cu), or a combinationthereof and is deposited using PVD or by lamination of a foil materialin some embodiments, for example. Alternatively, the seed layer 152 mayinclude other materials and may be formed using other methods.

After the formation of the seed layer 152, a photoresist P2 is appliedover the seed layer 152 and is then patterned. As a result, openings O4are formed in the photoresist P2 through which some portions of the seedlayer 152 are exposed. The photoresist P2 is patterned using lithographyto define the pattern for conductors 154 formed in a subsequent step.The conductors 154 are respectively formed in the openings O4 of thephotoresist P2 through, for example, plating which may be electroplating or electro-less plating. The conductors 154 are plated on theexposed portions of the seed layer 152. The conductors 154 may include ametal or a metal alloy including aluminum, copper, tungsten, and/oralloys thereof.

After the plating of the conductors 154, the photoresist P2 is removed,and some portions of the seed layer 152 are exposed. An etch step can beperformed to remove the exposed portions of the seed layer 152, and theetch step may include an anisotropic etching. Some portions of the seedlayer 152 that are covered by the conductors 154, on the other hand,remain not etched, and the resulting structure is shown in FIG. 8. Theconductors 154 and remaining portions of the seed layer 152 can becollectively referred to as redistribution lines (RDLs) 150. Althoughthe seed layer 152 is shown as a layer separate from the conductors 154,when the seed layer 152 is made of a material similar to orsubstantially the same as the respective overlying conductors 154, theseed layer 152 may be merged with the conductors 154 with nodistinguishable interface therebetween. In alternative embodiments,there exist distinguishable interfaces between the seed layer 152 andthe overlying conductors 154.

Reference is made to FIG. 9. A dielectric layer 160 is formed over theRDLs 150 such that the RDLs 150 are embedded in the dielectric layer160. The dielectric layer 160 may include a polymer, such as polyimide,benzocyclobutene (BCB), polybenzoxazole (PBO), or the like, and isdeposited using a spin coating process or a lamination process, asexamples. Alternatively, the dielectric layer 160 may includenon-organic dielectric materials, such as silicon oxide, siliconnitride, silicon carbide, silicon oxynitride, or the like. Thedielectric layer 160 is patterned using a lithography process. Forexample, a photoresist (not shown) may be formed over the dielectriclayer 160, and the photoresist is patterned by exposure to energy orlight reflect from or transmitted through a lithography mask having apredetermined pattern thereon. The photoresist is developed, and exposed(or unexposed, depending on whether the photoresist is positive ornegative) regions of the photoresist are removed using an ashing and/oretching process. The photoresist is then used as an etch mask during anetch process. Exposed portions of the dielectric layer 160 are removedduring the etch process to form openings O5 through which some portionsof the RDLs 150 are exposed.

The number of layers of RDLs and the number of dielectric layers are notlimited in various embodiments of the present disclosure. For example,after the structure of FIG. 9 is formed, another layer of RDLs 170 andanother dielectric layer 180, as illustrated in FIG. 10, may be formedover the RDLs 150 and the dielectric layer 160 through steps as shown inFIGS. 6-9. In order to simplify the description, the steps for formingthe RDLs 170 and the dielectric layer 180 will not described again.

Reference is made to FIG. 10. The dielectric layer 180 is patterned toform openings O6 to expose some portions of the RDLs 170. Thereafter, ablanket seed layer 192 is formed over the dielectric layer 180 and theexposed RDLs 170, as illustrated in FIG. 11.

Reference is made to FIG. 12. A photoresist P3 is applied over the seedlayer 192 and is then patterned. As a result, openings O7 are formed inthe photoresist P3 through which some portions of the seed layer 192 areexposed. Afterwards, conductors 194 are respectively formed in theopenings O7 of the photoresist P3 through plating which may be electroplating or electro-less plating. The conductors 194 are plated on theexposed portions of the seed layer 192. After the plating of theconductors 194, the photoresist P3 is removed to expose some portions ofthe seed layer 192.

Reference is made to FIG. 13. An etch operation is performed to removethe exposed portions of the seed layer 192, and the etch operation mayinclude an anisotropic etching. Some portions of the seed layer 192 thatare covered by the conductors 194, on the other hand, remain not etched.

The buffer layer 110, the dielectric layer 120, the RDLs 130, thedielectric layer 140, the RDLs 150, the dielectric layer 160, the RDLs170, the dielectric layer 180, the seed layer 192, and the conductors194 can be collectively referred to as a redistribution structure 102.In some embodiments, the buffer layer 110, the dielectric layers 120,140, 160, and 180 can be referred to as a dielectric structure 104 ofthe redistribution structure 102. The RDLs 130, 150, 170, the seed layer192, and the conductors 194 can be referred to as a wiring structure 106of the redistribution structure 102.

Reference is made to FIG. 14. A seed layer 212 is formed on theredistribution structure 102, for example, through PVD or metal foillaminating. The seed layer 212 may include copper, copper alloy,aluminum, titanium, titanium alloy, or combinations thereof. In someembodiments, the seed layer 212 includes a titanium layer and a copperlayer over the titanium layer. In alternative embodiments, the seedlayer 212 is a copper layer. Thereafter, a photoresist P4 is appliedover the seed layer 212 and is then patterned to expose some portions ofthe seed layer 212. As a result, openings O8 are formed in thephotoresist P4 through which some portions of the seed layer 212 areexposed.

Reference is made to FIG. 15. Conductors 214 are respectively formed inthe openings O8 of the photoresist P4 through, for example, platingwhich may be electro plating, electro-less plating, or metal-pasteprinting. The conductors 214 are plated on the exposed portions of theseed layer 212 underlying the openings O8, respectively. The conductors214 may include copper, aluminum, tungsten, nickel, solder, silver oralloys thereof. Top-view shapes of the conductors 214 may be rectangles,squares, circles, or the like. After the plating of the conductors 214,the photoresist P4 is removed, and some portions of the seed layer 212are exposed.

Reference is made to FIG. 16. An etch step is performed to remove theexposed portions of seed layer 212 that are not covered by theconductors 214, wherein the etch step may include an anisotropicetching. Some portions of the seed layer 212 that are covered by theconductors 214, on the other hand, remain not etched. Throughout thedescription, the conductors 214 and the remaining underlying portions ofthe seed layer 212 are in combination referred to as through integratedfan-out (InFO) vias (TIVs) 210, which are also referred to asthrough-vias. Although the seed layer 212 is shown as a layer separatefrom the conductors 214, when the seed layer 212 is made of a materialsimilar to or substantially the same as the respective overlyingconductors 214, the seed layer 212 may be merged with the conductors 214with no distinguishable interface therebetween. In alternativeembodiments, there exist distinguishable interfaces between the seedlayer 212 and the overlying conductors 214.

After the formation of the TIVs 210, some conductors 194 not covered bythe conductors 214 are exposed, so that subsequently placedsemiconductor devices 220 (see FIG. 17) can be electrically connected tothe redistribution structure 102 through the pre-exposed conductors 194.The method that forms the redistribution structure 102 before thesemiconductor devices 220 are placed can be referred to as a “RDL-first”process herein.

Reference is made to FIG. 17. The semiconductor devices 220 are disposedon or placed on the redistribution structure 102 using a pick-and-placemachine, manually, or the like. The number of the semiconductor devices220 is not limited in various embodiments of the present disclosure. Thethicknesses of the semiconductor devices 220 may be the same ordifferent, and various embodiments of the present disclosure are notlimited in this regard. The semiconductor devices 220 can beelectrically connected to some conductors 194 of the redistributionstructure 102 not covered by the TIVs 210. For example, bonding pads 224(such as copper pads) on the bottom portion of the semiconductor devices220 are electrically connected to the conductors 194. In other words,the semiconductor devices 220 are disposed on the redistributionstructure 102 using a “flip chip” approach; that is, the bonding pads224 on the face of the semiconductor devices 220 are “flipped” over sothey are “face down”, and the bonding pads 224 are connected to theconductors 194 with a conductive material. For example, the bonding pads224 can be electrically and mechanically connected to the exposedconductors 194 of the redistribution structure 102 through connectors226. In some embodiments, the conductors 194 are formed as pads, and theconnectors 226 may be solder bumps or solder balls, and these solderbumps or solder balls are in physical contact with the conductors 194 toform solder-on-pad (SOP) connections. In some other embodiments, theconductors 194 may be formed as traces, and the connectors 226 mayinclude non-solder metal bumps. These non-solder metal bumps may includecopper pillars and may include one or more layers including nickel,gold, palladium, or other suitable materials. These non-solder metalbumps (e.g., alternative forms of connector 226) and the conductors 194may be bonded by solder to form bump-on-trace (BOT) connections. By theSOP connections or BOT connections formed by the connectors 226, thesemiconductor devices 220 may be in electrical connection with theredistribution structure 102.

As shown in FIG. 17, in the structure formed by the “RDL-first” processaccording to some embodiments, an underfill layer 230 can be optionallyformed between the semiconductor device 220 and the redistributionstructure 102 and among the connectors 226. The underfill layer 230 maybe dispensed as a liquid using a capillary underfill (“CUF”) approach. Aresin or epoxy liquid is flowed beneath the semiconductor device 220 andfills the space between the semiconductor device 220 and theredistribution structure 102. Room temperature, UV, or thermal curingmay be used to cure the underfill layer 230. The underfill layer 230 canprovide mechanical strength and stress relief at least to the overlyingsemiconductor device 220 and the underlying redistribution structure102. In some embodiments, the underfill layer 230 is the same as asubsequently formed molding compound 250 (see FIG. 22) that molds thesemiconductor devices 220. That is, the space between the semiconductordevices 220 and the redistribution structure 102 may be filled by thesubsequently formed molding compound 250.

In some embodiments, the semiconductor devices 220 are unpackagedsemiconductor devices, such as logic device dies (e.g., acceleratedprocessing unit (APU), graphics processing unit (GPU), piezoelectricmultilayer actuator (PMA), piezoelectric actuator (PA), etc.), memorydevice dies (e.g., low power double-data-rate (LPDDR), Flash, highbandwidth memory (HBM), etc.), or sensor device dies (e.g., contactimage sensor (CIS), micro-electro-mechanical system (MEMS), etc.). Insome embodiments, the semiconductor devices 220 are designed for mobileapplications and may be central computing unit (CPU) dies, powermanagement integrated circuit (PMIC) dies, transceiver (TRX) dies, orthe like. The semiconductor device 220 includes a semiconductorsubstrate 222 (a silicon substrate, for example), and the bonding pads224 protrude from or level with a bottom dielectric layer (not shown) ofthe semiconductor device 220.

Reference is made to FIG. 18. The redistribution structure 102 isde-bonded from the carrier Cl. The adhesive layer A1 is also cleanedfrom the buffer layer 110 of the redistribution structure 102. As aresult of the removal of the adhesive layer Al, the buffer layer 110 ofthe redistribution structure 102 is exposed. In some embodiments, thestructure as shown in FIG. 18 is adhered to a dicing tape (not shown).In some embodiments, a laminating film (not shown) can be placed ontothe exposed buffer layer 110, wherein the laminating film may includeSR, ABF, backside coating tape, or the like. In alternative embodiments,no laminating film is placed over the buffer layer 110.

Reference is made to FIG. 19. The buffer layer 110 is patterned to formopenings O9 and hence the RDLs 130 are exposed. In some embodiments, alaser drilling process is performed to form the openings O9 to removeportions of the buffer layer 110 and portions of the seed layer 132.That is, the openings O9 can be referred to as laser drilled openings.The laser drilling process may create a jagged profile or a roughprofile of a sidewall of the opening 09. In some other embodiments,photolithography processes may also be used to form the openings O9 andremove portions of the buffer layer 110, and then an etch step isperformed to remove the exposed portions of the seed layer 132, in whichthe etch step may include an anisotropic etching. As a result, portionsof the conductors 134 are exposed through the openings O9. In someembodiments, the openings O9 are arranged in a grid pattern of rows andcolumns, so that conductive bumps (e.g., conductive balls 240)subsequently formed in the openings O9 can form the BGA.

The conductive balls 240 are formed on the exposed portions of the RDLs130. In other words, the conductive balls 240 are electrically connectedto the RDLs 130. As such, the conductive balls 240 can be electricallycoupled to the RDLs 150 via the RDLs 130. The formation of theconductive balls 240 may include placing solder balls in the openings O9of the buffer layer 110 and then reflowing the solder balls. Therefore,the conductive ball 240 is partially embeddedly retained in the opening09 of the buffer layer 110. After the formation of the conductive balls240, a singulation process is performed to saw the dielectric structure104 along lines L-L, such that at least one semiconductor assembly 100can be formed. In some embodiments where the assembly is adhered to adicing tape, the dicing tape can be removed after the singulationprocess.

After the formation of the conductive balls 240, an electrical test canbe performed to the redistribution structure 102, the semiconductordevices 220 and the TIVs 210, which may be beneficial to address someissues (e.g., defect/reliability) before molding the semiconductordevices 220 and the TIVs 210. In other words, the RDL-first process inaccordance with some embodiments of the present disclosure allows theelectrical test to be performed at an intermediate package through theconductive balls 240, as examples. In this way, the intermediatepackage, i.e. the semiconductor assembly 100, can be identified as aknown good package when it passes the electrical test. In addition, thesemiconductor assembly 100 is friendly to thermal-sensitivesemiconductor devices 220 because the redistribution structure 102 isformed before disposing the semiconductor devices 220, in which hightemperature processes are performed to form the redistribution structure102, thereby preventing the semiconductor devices 220 from beingdamaged.

FIG. 20 is a cross-sectional view of a semiconductor assembly 100 a inaccordance with some embodiments of the present disclosure. Thesemiconductor assembly 100 a may be formed by manufacturing steps of thesemiconductor assembly 100 as discussed previously. The semiconductorassembly 100 a has RDLs 130 a and less conductive balls 240 a than theconductive balls 240 of the semiconductor assembly 100. The RDLs 130 ais located in the dielectric layer 120 a and electrically connected tothe semiconductor device 220 a and the TIVs 210 a, and the conductiveballs 240 a are electrically connected to the RDLs 130 a. In someembodiments, the semiconductor assembly 100 a includes semiconductordevices 220 a, which are the same as the semiconductor devices 220 ofFIG. 19. In alternative embodiments, the semiconductor devices 220 a ofFIG. 20 are different from the semiconductor devices 220 of FIG. 19, andvarious embodiments of the present disclosure are not limited in thisregard.

After the formations of the semiconductor assembly 100 of FIG. 19 and atleast one semiconductor assembly 100 a of FIG. 20, the semiconductorassembly 100 a is bonded to the semiconductor assembly 100 through theconductive balls 240 a of the semiconductor assembly 100 a and the TIVs210 of the semiconductor assembly 100. The conductive balls 240 a arerespectively substantially aligned with the TIVs 210. As a result, thesemiconductor assembly 100 a can be stacked on the semiconductorassembly 100.

In some embodiments, TIVs 210 a of the semiconductor assembly 100 a arerespectively substantially aligned with the conductive balls 240 a. As aresult of such configuration, at least two semiconductor assemblies 100a can be stacked through the conductive balls 240 a of the uppersemiconductor assembly 100 a and the TIVs 210 a of the lowersemiconductor assembly 100 a.

FIGS. 21-22 are cross-sectional views of intermediate stages in themanufacturing the package structure after the step of FIG. 19. Referenceis made to FIG. 21. After the semiconductor assembly 100 and pluralsemiconductor assemblies 100 a are formed, one of the semiconductorassemblies 100 a is stacked on the semiconductor assembly 100 throughthe conductive balls 240 a at the bottom side of the semiconductorassembly 100 a and the TIVs 210 at the top side of the semiconductorassembly 100. As a result, the RDLs 130 a of the semiconductor assembly100 a are bonded to the RDLs 170 of the semiconductor assembly 100. Inother words, conductive features 215 including the TIVs 210 and theoverlying conductive balls 240 a electrically connect the RDLs 130 a ofthe semiconductor assembly 100 a and the RDLs 170 of the semiconductorassembly 100. In addition, conductive features 215a including the TIVs210 a and the overlying conductive balls 240 a electrically connect theRDLs 130 a through the RDLs 150 a. Thereafter, other semiconductorassemblies 100 a are sequentially stacked on the first stackedsemiconductor assembly 100 a through the conductive balls 240 a and theTIVs 210 a. In some embodiments, the semiconductor assemblies 100 a arethe same. In alternatively embodiments, the semiconductor assemblies 100a are different. For example, the semiconductor assemblies 100 a mayhave different kinds of semiconductor devices 220 a, different layers ofRDLs 150 a, and/or different layout of RDLs 150 a.

After the semiconductor assemblies 100 a are bonded to the semiconductorassembly 100, a semiconductor package 300 is bonded to the uppersemiconductor assembly 100 a. The semiconductor package 300 is over thestacked assemblies of the semiconductor assemblies 100 a and 100. Insome embodiments, the semiconductor package 300 includes a substrate 320and conductive bumps or conductive balls 330. The conductive bumps 330protrude from the substrate 320. In addition, the conductive bumps 330of the semiconductor package 300 are substantially aligned with the TIVs210 a of the upper semiconductor assembly 100 a, respectively. In suchconfiguration, the semiconductor package 300 can be bonded to the uppersemiconductor assembly 100 a through the conductive bumps 330 at thebottom side of the semiconductor package 300 and the TIVs 210 a at thetop side of the upper semiconductor assembly 100 a, and hence thesemiconductor package 300 is electrically connected to the underlyingTIVs 210 a through the conductive bumps 330. However, variousembodiments of the present disclosure are not limited to the sequence ofthe aforementioned steps. For example, the semiconductor assemblies 100a are jointed to form a stacked structure, and then the semiconductorpackage 300 is bonded to the top side of the stacked structure.Thereafter, the lower side of the stacked structure is bonded to thesemiconductor assembly 100, such that the structure of FIG. 21 may bealso obtained. In some embodiments, the semiconductor package 300 may bememory devices, such as a static random access memory (SRAM) or dynamicrandom access memory (DRAM) device. The semiconductor package 300 mayinclude a plurality of stacked memory dies therein. Moreover, othertypes of the semiconductor package 300 may be present on thesemiconductor assembly 100 a as well, and various embodiments of thepresent disclosure are not limited in this regard.

Reference is made to FIG. 22. After the formation of the stackedstructure as shown in FIG. 21, a molding material (or molding compound)250 molds the semiconductor devices 220, 220 a, the TIVs 210, 210 a, andthe conductive balls 240 a, 330. The semiconductor package 300 is overthe molding material 250. In other words, the molding material 250 isformed between the semiconductor assembly 100 and the overlyingsemiconductor assembly 100 a, between two adjacent semiconductorassemblies 100 a, and between the semiconductor package 300 and theunderlying semiconductor assembly 100 a. Furthermore, the moldingmaterial 250 surrounds the semiconductor devices 220, 220 a, the TIVs210, 210 a, and the conductive balls 240 a, 330. The molding material250 fills gaps between the semiconductor devices 220 and the TIVs 210and fills gaps between the semiconductor devices 220 a and the TIVs 210a. In addition, the molding material 250 has a portion between thesemiconductor device 220 and the dielectric layer 120 a (or the bufferlayer 110 a). The TIVs 210, the conductive balls 240 a, and the TIVs 210a are in contact with the molding material 250. The molding material 250may be in contact with the dielectric layer 180, the dielectric layer160 a, the buffer layer 110 a, and the substrate 320. After theformation of the molding material 250, the semiconductor assembly 100and the overlying molding material 250 forms a TIV package 410, and thesemiconductor assemblies 100 a and the overlying molding materials 250form TIV packages 410 a. Therefore, a combination of the TIV package410, the TIV packages 410 a, and the semiconductor package 300 forms apackage structure 400, and the resulting structure is shown in FIG. 22.

In some embodiments, the molding material 250 includes a polymer-basedmaterial. The term “polymer” can represent thermosetting polymers,thermoplastic polymers, or any mixtures thereof. The polymer-basedmaterial can include, for example, plastic materials, epoxy resin,polyimide, polyethylene terephthalate (PET), polyvinyl chloride (PVC),polymethylmethacrylate (PMMA), polymer components doped with fillersincluding fiber, clay, ceramic, inorganic particles, or any combinationsthereof.

Because one molding step can enable the molding material 250 to fillgaps between the semiconductor assembly 100 and the overlyingsemiconductor assembly 100 a, between two adjacent semiconductorassemblies 100 a, and between the semiconductor package 300 and theunderlying semiconductor assembly 100 a, cycle time and warpage infabricating the package structure 400 can be reduced.

In addition, when the package structure 400 is disposed on a printedcircuit board (PCB), the package structure 400 occupies an area of thePCB the same as that of the semiconductor assembly 100, thesemiconductor assemblies 100 a, or the semiconductor package 300, andhence the area of the PCB occupied by the semiconductor assemblies 100,100 a and the semiconductor package 300 can be reduced.

Since the package structure 400 is a three-dimensional package onpackage (POP) structure, performance of a system on which the packagestructure 400 is disposed may be improved due to short-length andhigh-bandwidth communications among the TIV packages 410, 410 a, and thesemiconductor package 300. Moreover, the package structure 400 mayinclude various semiconductor devices (e.g., 220 and 220 a) and thesemiconductor package 310, so as to be flexibly used by designers.

In some embodiments, the TIV package 410 has more semiconductor devices220 therein, and at least one of the TIV packages 410 a has moresemiconductor devices 220 a therein. As a result of such configuration,the number of layers of the TIV packages 410 a can be decreased but thepackage structure 400 may still have the same function. Moreover, thetotal height of the package structure 400 can be reduced.

FIG. 23 is a cross-sectional view of a package structure 400 a inaccordance with some embodiments of the present disclosure. The packagestructure 400 a includes the TIV package 410, the TIV packages 410 a,and an overlying TIV package 410 b. The difference between the TIVpackage 410 b and one of the TIV packages 410 a is that there is no TIV210 a and underlying conductors 194a in the TIV package 410 b.Conductive balls 240 b of the TIV package 410 b are substantiallyaligned with the underlying TIVs 210 a of the TIV package 410 a, andhence the conductive balls 240 b of the TIV package 410 b can berespectively bonded to the underlying TIVs 210 a of the TIV package 410a.

FIGS. 24-32 are cross-sectional views of intermediate stages in themanufacturing of a package structure in accordance with some embodimentsof the present disclosure. Reference is made to FIG. 24. Aredistribution structure 102 a including the dielectric structure 104and a wiring structure 106 a is formed on the carrier C1. The formationof the redistribution structure 102 a is similar to that of theredistribution structure 102 described above from FIGS. 1 to 13, andwill not be repeated in the following description. The pattern of thewiring structure 106 a of FIG. 24 is different from that of the wiringstructure 106 of FIG. 13, but various embodiments of the presentdisclosure are not limited in this regard.

Reference is made to FIG. 25. Conductive features 265 include passiveinterposers 260 and conductive bumps 266. In some embodiments, thepassive interposers 260 are through silicon via (TSV) devices. Thesemiconductor devices 220 and TSV devices 260 are disposed on or placedon the redistribution structure 102 a using a pick-and-place machine,manually or other suitable methods. The TSV devices 260 are over thedielectric layer 180, and TSVs 268 are in the TSV devices 260 andelectrically connected to contact pads 264. The conductive bumps 266 arebetween and electrically connect the TSV device 260 and the RDLs 170.The number of the semiconductor devices 220 and the number of the TSVdevices 260 are not limited in various embodiments of the presentdisclosure. The semiconductor devices 220 and the TSV devices 260 can beelectrically connected to the conductors 194 of the redistributionstructure 102 a. The bonding pads 224 of the semiconductor devices 220and the contact pads 264 of the TSV devices 260 are connected to theconductors 194 with conductive material. For example, the bonding pads224 can be electrically and mechanically connected to some of theconductors 194 through the connectors 226, e.g. conductive bumps, andthe contact pads 264 can be electrically and mechanically connected tothe other conductors 194 through the conductive bumps 266.

As shown in the assembly of FIG. 25, in the structure formed by the“RDL-first” process according to some embodiments, the underfill layer230 can be optionally formed between the semiconductor device 220 andthe redistribution structure 102 a and among the connectors 226, and canbe optionally formed between the TSV devices 260 and the redistributionstructure 102 a and among the conductive balls 266.

In some embodiments, the TSV devices 260 may include, for example,through silicon vias (TSVs) 268 and integrated passive devices (IPDs,not shown). The TSV devices 260 allow a higher density of structures,such as TSVs 268 and/or IPDs, to be formed therein. In some embodiments,the TSV device 260 comprises a substrate 261 comprise a semiconductormaterial, such as silicon or the like. Holes in the substrate 261 can befilled with conductors to form TSVs 268 and IPDs, such as trenchcapacitors. The TSV device 260 comprises an interconnect layer 262 whichincludes one or more layers of dielectric material with conductivefeatures formed therein. In some embodiment, the layers of dielectricmaterial in the interconnect layer 262 are formed of a photo-sensitivematerial such as polybenzoxazole (PBO), polyimide (PI), benzocyclobutene(BCB), or the like. In alternative embodiments, the layers of dielectricmaterial in the interconnect layer 262 may be formed of a nitride suchas silicon nitride, an oxide such as silicon oxide, phosphosilicateglass (PSG), borosilicate glass (BSG), boron-doped phosphosilicate glass(BPSG), or the like. In some alternative embodiments, the interconnectlayer 262 may comprise an interposer or packaging substrate, such as asilicon interposer, organic substrate, a laminate substrate (e.g., a1-2-1 laminate substrate), or the like. The interconnect layer 262provides electrical connections between opposing sides and may act as anRDL structure. A set of external contact pads 264 provide an externalelectrical connection using, for example, conductive bumps 266.

As illustrated, a pitch between neighboring TSVs 268 is shorter than apitch of neighboring TIVs (e.g. TIV 210 or 210 a as describedpreviously), and therefore, if the TSVs 268 are to be bonded with bumps,the TSVs 268 with shorter pitch allow higher density of the bumps.

Reference is made to FIG. 26. A molding material (or molding compound)250 a is molded on the redistribution structure 102 a, the semiconductordevices 220, and the TSV devices 260. The molding material 250 a fillsgaps between the semiconductor devices 220 and the TSV devices 260 andmay be in contact with the redistribution structure 102 a, such as thedielectric layer 180 of the redistribution structure 102 a. The topsurface of the molding material 250 a is higher than the top surfaces ofthe semiconductor devices 220 and the TSV devices 260.

In some embodiments, the molding material 250 a includes a polymer-basedmaterial. The term “polymer” can represent thermosetting polymers,thermoplastic polymers, or any mixtures thereof. The polymer-basedmaterial can include, for example, plastic materials, epoxy resin,polyimide, polyethylene terephthalate (PET), polyvinyl chloride (PVC),polymethylmethacrylate (PMMA), polymer components doped with fillersincluding fiber, clay, ceramic, inorganic particles, or any combinationsthereof.

Reference is made to FIG. 27. Next, a planarization process, such asgrinding, is performed to thin the molding material 250 a, until the topsurfaces of the semiconductor devices 220 and the TSV devices 260 areexposed. The molding material 250 a surrounds the semiconductor devices220 and the TSV devices 260. In some embodiments, the TSVs 268 on thetop surfaces of the TSV devices 260 are also exposed after the grindingthe molding material 250 a. The resulting structure is shown in FIG. 27,in which the molding material 250 a is in contact with sidewalls of thesemiconductor devices 220 and the TSV devices 260. Due to the grinding,the top surfaces of the semiconductor devices 220 are substantiallylevel (coplanar) with top surfaces of the TSV devices 260, and aresubstantially level (coplanar) with the top surface of the moldingmaterial 250 a. As a result of the grinding, conductive residues such asmetal particles may be generated, and left on the top surface of thestructure shown in FIG. 27. Accordingly, after the grinding, a cleaningmay be performed, for example, through a wet etching, so that theconductive residues are removed.

Reference is made to FIG. 28. Next, a molded package 510 is de-bondedfrom the carrier C1. The adhesive layer A1 is also cleaned from themolded package 510. As a result of the removal of the adhesive layer Al,the buffer layer 110 is exposed. Referring to FIG. 28, the moldedpackage 510 with the semiconductor devices 220, the molding material 250a, and the TSV devices 260 thereon is further adhered to a dicing tapeDT, wherein the molding material 250 a faces toward, and may contact,the dicing tape DT. In some embodiments, a laminating film (not shown)is placed onto the exposed buffer layer 110, wherein the laminating filmmay include an ajinomoto buildup film (ABF), a solder resist film (SR),backside coating tape, or the like. In alternative embodiments, nolaminating film is placed over the buffer layer 110.

Openings O10 are formed in the buffer layer 110. After the formation ofthe openings O10 of the buffer layer 110, portions of the seed layer 132of the RDLs 130 are exposed through the openings O10. In someembodiments, a laser drilling process is performed to form the openingsO10. In some other embodiments, photolithography processes may also beused to form the openings O10. Thereafter, an etch step is performed toremove the exposed portions of the seed layer 132, in which the etchstep may include an anisotropic etching. As a result, portions of theconductors 134 underlying the seed layer 132 are exposed through theopenings O10, so as to receive subsequently formed the conductive balls240 (see FIG. 29). In some embodiments, the openings O10 are arranged ina grid pattern of rows and columns, so that the conductive balls 240subsequently formed in the openings O10 can form a ball grid array (BGA).

Reference is made to FIG. 29. Conductive bumps, such as the conductiveballs 240, are formed on the exposed portions of the conductors 134. Inother words, the conductive balls 240 are respectively in contact withthe conductors 134, so that the conductive balls 240 can be electricallyconnected to the conductors 134. As such, the conductive balls 240 canbe electrically coupled to the wiring structure 106 a via the conductors134. The formation of the conductive balls 240 may include placingsolder balls in the openings O10, and then reflowing the solder balls.

After the conductive balls 240 are formed, a singulation process iscarried out to saw the dielectric structure 104 and the molding material250 a along lines L1, and the dicing tape DT can be removed as well,such that plural chip-scale molded packages 510 may be formed.

In alternative embodiments, after the carrier C1 is de-bonded and theadhesive layer A1 is cleaned, one or more etch operations are carriedout to remove the buffer layer 110 and horizontal portions of the seedlayers 132 until the conductors 134 are exposed. The resulting structureis shown in FIG. 30, in which top surfaces of the RDLs 130 are exposedand substantially level with a top surface of the remaining dielectriclayer 120. After the etching process, the conductive balls 240 areformed on the exposed RDLs 130, and resulting structure is shown in FIG.31.

After the conductive balls 240 are formed, a singulation process iscarried out to saw the dielectric structure 104 and the molding material250 a along lines L1, and the dicing tape DT can be removed as well,such that plural chip-scale molded packages 510 may be formed, and theresulting structure is shown in FIG. 32. In the following description,the RDLs 130, the conductive balls 240, and the dielectric layer 120shown in FIG. 31 are formed in packages as shown in FIGS. 32-35. In somealternative embodiments, the RDLs 130, the conductive balls 240, thebuffer layer 110, and the dielectric layer 120 shown in FIG. 29 can beformed in packages as shown in FIGS. 32-35, and the various embodimentsof the present disclosure are not limited in this regard.

FIG. 33 is a cross-sectional view of a molded package 510 a inaccordance with some embodiments of the present disclosure. The moldedpackage 510 a may be formed by aforementioned manufacturing steps of themolded package 510. Compared with the molded package 510, the moldedpackage 510 a has the RDLs 130 a therein, and has the conductive balls240 a that are substantially aligned with the overlying TSV devices 260of the molded package 510, respectively. In some embodiments, the moldedpackage 510 a includes the semiconductor devices 220 a and TSV devices260 a respectively the same as the semiconductor devices 220 and the TSVdevices 260 of FIG. 32. In alternative embodiments, the semiconductordevices 220 a and the TSV devices 260 a are respectively different fromthe semiconductor devices 220 and the TSV devices 260 of FIG. 32, andvarious embodiments of the present disclosure are not limited in thisregard.

FIG. 34 is a cross-sectional view of a molded package 510 b inaccordance with some embodiments of the present disclosure. In someembodiments, the TSV devices 260 a of FIG. 29 are optional. The moldedpackage 510 b has no TSV device in the molding material 250 a, but hasmore molding material 250 a on the dielectric layer 160 a to supplementvacancies.

FIG. 35 is a cross-sectional view of a package structure 500 inaccordance with some embodiments of the present disclosure. After theformations of the molded package 510 of FIG. 32, at least one moldedpackage 510 a of FIG. 33, and the molded package 510 b of FIG. 34, themolded package 510 b is bonded to the molded package 510 a through theconductive balls 240 a of the molded package 510 b and the TSV devices260 a of the underlying molded package 510 a, and the molded package 510a is bonded to the molded package 510 through the conductive balls 240 aof the molded package 510 a and the TSV devices 260 of the moldedpackage 510. The conductive balls 240 a are between and electricallyconnect the TSV devices 260 of the molded package 510 and the RDLs 130 aof the molded package 510 a. Therefore, the conductive balls 240 a ofthe molded package 510 b are electrically connected to the TSVs 268 ofthe TSV devices 260 a of the molded package 510 a, and the conductiveballs 240 a of the molded package 510 a are electrically connected tothe TSVs 268 of the TSV devices 260 of the molded package 510. In otherwords, the conductive features 265 including the TSV devices 260, theconductive balls 266, and the conductive balls 240 a electricallyconnect the RDLs 130 a of the molded package 510 a and the RDLs 170 ofthe molded package 510. In addition, conductive features 265a includingthe TSV devices 260 a, the conductive balls 266 a, and the conductiveballs 240 a electrically connect the RDLs 130 a through the RDLs 150 a.As a result of such configuration, the molded package 510 b is stackedon the molded package 510 a, and the molded package 510 a is stacked onthe molded package 510, thereby forming the package structure 500.

In some embodiments, the TSV devices 260 a of the molded package 510 aare substantially aligned with the conductive balls 240 a of the moldedpackage 510 a, and hence at least two molded package 510 a can bestacked through the conductive balls 240 a of the upper molded package510 a and the TSV devices 260 a of the lower molded package 510 a. Forexample, the package structure 500 includes three molded packages 510 a,but various embodiments of the present disclosure are not limited inthis regard.

In some embodiments, underfills UF are optionally disposed between themolded package 510 b and the underlying molded package 510 a, betweentwo adjacent molded packages 510 a, and between the molded packages 510a and the underlying molded package 510, such that the molded package510 b is securely positioned on the molded package 510 a, and the moldedpackage 510 a is securely positioned on another molded package 510 a orthe molded package 510.

FIGS. 36-51 are cross-sectional views of intermediate stages in themanufacturing of a package structure in accordance with some embodimentsof the present disclosure. Reference is made to FIG. 36. An adhesivelayer A3 is formed on a carrier C3. The carrier C3 may be a blank glasscarrier, a blank ceramic carrier, or the like. The adhesive layer A3 maybe made of an adhesive, such as ultra-violet (UV) glue, light-to-heatconversion (LTHC) glue, or the like, although other types of adhesivesmay be used. A buffer layer 610 is formed over the adhesive layer A3.The buffer layer 610 is a dielectric layer, which may be a polymerlayer. The polymer layer may include, for example, polyimide,polybenzoxazole (PBO), benzocyclobutene (BCB), an ajinomoto buildup film(ABF), a solder resist film (SR), or the like.

Reference is made to FIG. 37. A seed layer 623 is formed on the bufferlayer 610, for example, through physical vapor deposition (PVD) or metalfoil laminating. The seed layer 623 may include copper, copper alloy,aluminum, titanium, titanium alloy, or combinations thereof. In someembodiments, the seed layer 623 includes a titanium layer and a copperlayer over the titanium layer. In alternative embodiments, the seedlayer 623 is a copper layer.

Reference is made to FIG. 38. A photo resist P11 is applied over theseed layer 623 and is then patterned. As a result, openings O11 areformed in the photo resist P11, through which some portions of the seedlayer 623 are exposed.

Reference is made to FIG. 39. Conductors 625 are formed in the photoresist P11 through plating, which may be electro plating or electro-lessplating. The conductors 625 are plated on the exposed portions of theseed layer 623. The conductors 625 may include copper, aluminum,tungsten, nickel, solder, or alloys thereof. Heights of the conductors625 are determined by the thickness of subsequently placed semiconductordevices 630 (see FIG. 42), with the heights of the conductors 625greater than the thickness of the semiconductor devices 630 in someembodiments of the present disclosure. After the plating of theconductors 625, the photo resist P11 is removed, and the resultingstructure is shown in FIG. 40. After the photo resist P11 is removed,some portions of the seed layer 623 are exposed.

Reference is made to FIG. 41. An etch step is performed to remove theexposed portions of seed layer 623, wherein the etch step may include ananisotropic etching. Some portions of the seed layer 623 that arecovered by the conductors 625, on the other hand, remain not etched.Throughout the description, the conductors 625 and the remainingunderlying portions of the seed layer 623 are in combination referred toas conductive features 620, which are through integrated fan-out (InFO)vias (TIVs), which are also referred to as through-vias. Although theseed layer 623 is shown as a layer separate from the conductors 625,when the seed layer 623 is made of a material similar to orsubstantially the same as the respective overlying conductors 625, theseed layer 623 may be merged with the conductors 625 with nodistinguishable interface therebetween. In alternative embodiments,there exist distinguishable interfaces between the seed layer 623 andthe overlying conductors 625.

FIG. 42 illustrates placement of the semiconductor devices 630 over thebuffer layer 610. The semiconductor devices 630 may be adhered to thebuffer layer 610 through adhesive layers 631. In some embodiments, thesemiconductor devices 630 are unpackaged semiconductor devices, i.e.device dies. For example, the semiconductor devices 630 may be logicdevice dies including logic transistors therein. In some embodiments,the semiconductor devices 630 are designed for mobile applications, andmay be central computing unit (CPU) dies, power management integratedcircuit (PMIC) dies, transceiver (TRX) dies, or the like. Each of thesemiconductor devices 630 includes a semiconductor substrate 632 (asilicon substrate, for example) that contacts the adhesive layer 631,wherein the back surface of the semiconductor substrate 632 is incontact with the adhesive layer 631.

In some embodiments, conductive pillars 636 (such as copper posts) areformed as the top portions of the semiconductor devices 630, and areelectrically coupled to the devices such as transistors (not shown) inthe semiconductor devices 630. In some embodiments, a dielectric layer634 is formed on the top surface of the respective semiconductor device630, with the conductive pillars 636 having at least lower portions inthe dielectric layer 634. The top surfaces of the conductive pillars 636may be substantially level with the top surfaces of the dielectriclayers 634 in some embodiments. Alternatively, the dielectric layers arenot formed, and the conductive pillars 636 protrude from a topdielectric layer (not shown) of the respective semiconductor devices630.

Reference is made to FIG. 43. A molding material 635 is molded on thesemiconductor devices 630 and the TIVs 620. The molding material 635fills gaps between the semiconductor devices 630 and the TIVs 620, andmay be in contact with the buffer layer 610. Furthermore, the moldingmaterial 635 is filled into gaps between the conductive pillars 636 whenthe conductive pillars 636 are protruding metal pillars (thisarrangement is not shown). The top surface of the molding material 635is higher than the top ends of the conductive pillars 636 and the TIVs620.

In some embodiments, the molding material 635 includes a polymer-basedmaterial. The term “polymer” can represent thermosetting polymers,thermoplastic polymers, or any mixtures thereof. The polymer-basedmaterial can include, for example, plastic materials, epoxy resin,polyimide, polyethylene terephthalate (PET), polyvinyl chloride (PVC),polymethylmethacrylate (PMMA), polymer components doped with fillersincluding fiber, clay, ceramic, inorganic particles, or any combinationsthereof.

Next, a grinding step is performed to thin the molding material 635,until the conductive pillars 636 and the TIVs 620 are exposed. Theresulting structure is shown in FIG. 44, in which the molding material635 is in contact with sidewalls of the semiconductor devices 630 andthe TIVs 620. The molding material 635 surrounds the semiconductordevices 630 and the TIVs 620. Due to the grinding, the top ends of theTIVs 620 are substantially level (coplanar) with the top ends of theconductive pillars 636, and are substantially level (coplanar) with thetop surface of the molding material 635. As a result of the grinding,conductive residues such as metal particles may be generated, and lefton the top surface of the structure shown in FIG. 44. Accordingly, afterthe grinding, a cleaning may be performed, for example, through a wetetching, so that the conductive residues are removed.

Reference is made to FIG. 45. A dielectric layer 640 is formed over theTIVs 620, the molding material 635, and the semiconductor devices 630.The dielectric layer 640 may include a polymer such as polyimide,benzocyclobutene (BCB), polybenzoxazole (PBO), or the like, which isdeposited using a spin coating process or a lamination process, asexamples. Alternatively, the dielectric layer 640 may includenon-organic dielectric materials such as silicon oxide, silicon nitride,silicon carbide, silicon oxynitride, or the like. The dielectric layer640 is patterned using a lithography process. For example, a photoresist(not shown) may be formed over the dielectric layer 640, and thephotoresist is patterned by exposure to energy or light reflect from ortransmitted through a lithography mask having a predetermined patternthereon. The photoresist is developed, and exposed (or unexposed,depending on whether the photoresist is positive or negative) regions ofthe photoresist are removed using an ashing and/or etching process. Thephotoresist is then used as an etch mask during an etch process. Exposedportions of the dielectric layer 640 are removed during the etch processto form openings O12, through which the TIVs 620 and the conductivepillars 636 are exposed. Afterwards, the photoresist is removed.

Reference is made to FIG. 46. A seed layer 652 is formed over thedielectric layer 640 and in the openings O12 of the dielectric layer640. In some embodiments, the seed layer 652 is conformally formed onthe dielectric layer 640 and in the openings O12. The seed layer 652includes about 0.3 μm of a material such as titanium (Ti), copper (Cu),or a combination thereof deposited using PVD or by lamination of a foilmaterial in some embodiments, for example. Alternatively, the seed layer652 may include other materials and dimensions and may be formed usingother methods.

After the formation of the seed layer 652, a photoresist P12 is appliedover the seed layer 652 and is then patterned. As a result, openings O13are formed in the photoresist P12, through which some portions of theseed layer 652 are exposed. The photoresist P12 is patterned usinglithography to further define the pattern for conductors 654 formed in asubsequent step. The conductors 654 are respectively formed in theopenings O13 of the photoresist P12 through, for example, plating, whichmay be electro plating or electro-less plating. The conductors 654 areplated on the exposed portions of the seed layer 652. The conductors 654may include a metal or a metal alloy including aluminum, copper,tungsten, and/or alloys thereof.

After the plating of the conductors 654, the photoresist P12 is removed,and some portions of the seed layer 652 are exposed. An etch step can beperformed to remove the exposed portions of the seed layer 652, and theetch step may include an anisotropic etching. Some portions of the seedlayer 652 that are covered by the conductors 654, on the other hand,remain not etched, and the resulting structure is shown in FIG. 47. Theconductors 654 and remaining portions of the seed layer 652 can becollectively referred to as redistribution lines (RDLs) 650. Althoughthe seed layer 652 is shown as a layer separate from the conductors 654,when the seed layer 652 is made of a material similar to orsubstantially the same as the respective overlying conductors 654, theseed layer 652 may be merged with the conductors 654 substantially freefrom distinguishable interface therebetween. In alternative embodiments,there exist distinguishable interfaces between the seed layer 652 andthe overlying conductors 654.

Reference is made to FIG. 48. A dielectric layer 640 a is formed overthe RDLs 650 and the dielectric layer 640 such that the RDLs 650 areembedded in the dielectric layer 640 a. The dielectric layer 640 a mayinclude a polymer such as polyimide, benzocyclobutene (BCB),polybenzoxazole (PBO), or the like, which is deposited using a spincoating process or a lamination process, as examples. Alternatively, thedielectric layer 640 a may include non-organic dielectric materials suchas silicon oxide, silicon nitride, silicon carbide, silicon oxynitride,or the like. The dielectric layer 640 a is patterned using a lithographyprocess. For example, a photoresist (not shown) may be formed over thedielectric layer 640 a, and the photoresist is patterned by exposure toenergy or light reflect from or transmitted through a lithography maskhaving a predetermined pattern thereon. The photoresist is developed,and exposed (or unexposed, depending on whether the photoresist ispositive or negative) regions of the photoresist are removed using anashing and/or etching process. The photoresist is then used as an etchmask during an etch process. Exposed portions of the dielectric layer640 a are removed during the etch process to form openings O14, throughwhich some portions of the RDLs 650 are exposed.

The number of layers of RDLs and the number of dielectric layers are notlimited in various embodiments of the present disclosure. For example,after the structure of FIG. 48 is formed, layers of RDLs 650 a, 650 band dielectric layers 640 b, 640 c as illustrated in FIG. 49, may beformed over the RDLs 650 and the dielectric layer 640 a through theaforementioned steps from FIG. 45 to FIG. 48. In order to simplify thedescription, the steps for forming the RDLs 650 a, 650 b and thedielectric layers 640 b, 640 c will not described again. Moreover, theformation of contact pads 660 of FIG. 49 is similar to the steps fromFIG. 3 to FIG. 5.

Reference is made to FIG. 49. After the dielectric layer 640 c ispatterned to form openings, a seed layer 662 is formed over thedielectric layer 640 c and exposed portions of the RDLs 650 b in theopenings, and then a photoresist is applied over the seed layer 662 andis patterned to form openings. Next, conductors 664 are respectivelyformed in the openings of the photoresist through plating, such that theconductors 664 are plated on the exposed portions of the seed layer 662.After the plating of the conductors 664, the photoresist is removed toexpose some portions of the seed layer 662, and then an etch operationis performed to remove the exposed portions of the seed layer 662. As aresult, the conductors 664 and the remaining underlying portions of theseed layer 662 are in combination referred to as the contact pads 660 ofFIG. 49.

Although the seed layer 662 is shown as a layer separate from theconductors 664, when the seed layer 662 is made of a material similar toor substantially the same as the respective overlying conductors 664,the seed layer 662 may be merged with the conductors 664 substantiallyfree from distinguishable interface therebetween. In alternativeembodiments, there exist distinguishable interfaces between the seedlayer 662 and the overlying conductors 664.

Reference is made to FIG. 50. Conductive bumps, such as the conductiveballs 670, are formed on the contact pads 660. In other words, theconductive balls 670 are respectively in contact with the contact pads660, so that the conductive balls 670 can be electrically connected tothe contact pads 660. As such, the conductive balls 670 can beelectrically coupled to the RDLs 650, 650 a, 650 b via the contact pads660. After the conductive balls 670 are formed, the carrier C3 and theadhesive layer A3 are removed from the buffer layer 610.

Reference is made to FIG. 51. As a result of the de-bonding from thecarrier C3 and removal of the adhesive layer A3, the buffer layer 610over the semiconductor devices 630 and the molding material 635 isexposed. The buffer layer 610 is then patterned to form openings O15 andhence the TIVs 620 are exposed. In some embodiments, a laser drillingprocess is performed to form the openings O15. In some otherembodiments, photolithography processes may also be used to form theopenings O15 and remove portions of the buffer layer 610. In someembodiments, the structure shown in FIG. 50 can be adhered to a dicingtape (not shown) after the de-bonding from the carrier C3. Next, asingulation process is carried out to saw the buffer layer 610, themolding material 635, and the dielectric layers 640, 640 a-640 c alonglines L2, such that plural chip-scale TIV packages 600 may be formed,and the resulting structure is shown in FIG. 52.

FIG. 53 is a cross-sectional view of a TIV package 600 a in accordancewith some embodiments of the present disclosure. The TIV package 600 amay be formed by aforementioned manufacturing steps of the TIV package600 of FIG. 52. Compared with the TIV package 600, the TIV package 600 ahas less conductive balls 670 a. In some embodiments, the TIV package600 a includes semiconductor devices 630 a the same as the semiconductordevices 630 of FIG. 52. In alternative embodiments, the semiconductordevices 630 a of FIG. 53 are different from the semiconductor devices630 of FIG. 52, and various embodiments of the present disclosure arenot limited in this regard.

FIG. 54 is a cross-sectional view of a package structure 700 inaccordance with some embodiments of the present disclosure. After theformations of the TIV package 600 of FIG. 52 and at least one TIVpackage 600 a of FIG. 53, the TIV package 600 a is bonded to the TIVpackage 600 through the conductive balls 670 a of the TIV package 600 a.The conductive balls 670 a are between the RDLs 650 b of the TIV package600 a and the TIVs 620 of the TIV package 600 and free from the moldingmaterial 635. The conductive balls 670 a of the TIV package 600 a arerespectively substantially aligned with the TIVs 620 of the TIV package600 that are respectively exposed through the openings O15 (see FIG.51). As a result, the TIV package 600 a can be stacked on the TIVpackage 600. In some embodiments, in the TIV package 600 a, the TIVs 620a are respectively substantially aligned with the conductive balls 670a. As a result of such configuration, at least two TIV packages 600 acan be stacked through the conductive balls 670 a of the upper TIVpackages 600 a and the exposed TIVs 620 a of the lower TIV packages 600a. In some embodiments, an underfill can be disposed between neighboringTIV packages and enclosing the conductive balls 670 a.

After the TIV packages 600 a are bonded to the TIV package 600, asemiconductor package 300 is bonded to the upper TIV package 600 a. Insome embodiments, the semiconductor package 300 includes the bufferlayer 320 and the conductive balls 330. The conductive balls 330protrude from the buffer layer 320. In addition, the conductive balls330 of the semiconductor package 300 are substantially aligned with theTIVs 620 a of the upper TIV package 600 a, respectively. In suchconfiguration, the semiconductor package 300 can be bonded to the upperTIV package 600 a through the conductive balls 330 at the bottom side ofthe semiconductor package 300 and the TIVs 620 a at the top side of theupper TIV package 600 a. However, various embodiments of the presentdisclosure are not limited to the sequence of the aforementioned steps.For example, the TIV packages 600 a are jointed to form a stackedstructure, and then the semiconductor package 300 is bonded to the topside of the stacked structure. Thereafter, the lower side of the stackedstructure is bonded to the TIV package 600, such that the packagestructure 700 of FIG. 54 may be also obtained. In some embodiments, thesemiconductor package 300 may be memory devices, such as a static randomaccess memory (SRAM) or dynamic random access memory (DRAM) device. Thesemiconductor package 300 may include a plurality of stacked memory diestherein. Moreover, other types of the semiconductor package 300 may bepresent on the TIV package 600 a as well, and various embodiments of thepresent disclosure are not limited in this regard.

In the aforementioned package structure, since the package structure isa three-dimensional package on package (POP) structure, performance of asystem on which the package structure is disposed may be improved due toshort-length and high-bandwidth communications among the TIV packagesand the semiconductor package. Moreover, the package structure mayinclude various semiconductor devices and the semiconductor package, soas to be flexibly used by designers.

According to some embodiments, a package structure includes a firstdielectric layer, a first semiconductor device over the first dielectriclayer, a first redistribution line in the first dielectric layer, asecond dielectric layer over the first semiconductor device, a secondsemiconductor device over the second dielectric layer, a secondredistribution line in the second dielectric layer, a conductivethrough-via over the first dielectric layer and electrically connectedto the first redistribution line, a conductive ball over the conductivethrough-via and electrically connected to the second redistributionline, and a molding material. The molding material surrounds the firstsemiconductor device, the conductive through-via, and the conductiveball, wherein a top of the conductive ball is higher than a top of themolding material.

According to some embodiments, a package structure includes a firstdielectric layer, a first semiconductor device over the first dielectriclayer, a first redistribution line in the first dielectric layer, aconductive through-via over the first dielectric layer and electricallyconnected to the first redistribution line, a molding materialsurrounding the first semiconductor device and the conductivethrough-via, a conductive ball over the conductive through-via, a seconddielectric layer over the molding material, a second semiconductordevice over the second dielectric layer, a second redistribution line inthe second dielectric layer and electrically connected to the conductiveball, and a buffer layer in contact with the conductive ball and spacedapart from the second dielectric layer.

According to some embodiments, a method includes forming a firstconductive through-via over a first buffer layer; disposing a firstsemiconductor device over the first buffer layer; forming a firstmolding material to surround the first semiconductor device and thefirst conductive through-via; forming a first redistribution lineelectrically connected to a first end of the first conductivethrough-via and the first semiconductor device, such that the firstbuffer layer, the first conductive through-via, the first semiconductordevice, the first molding material, and the first redistribution lineform a first package; forming a first conductive ball over andelectrically connected to the first redistribution line; forming asecond conductive through-via over a second buffer layer; disposing asecond semiconductor device over the second buffer layer; forming asecond molding material to surround the second semiconductor device andthe second conductive through-via; forming a second redistribution lineelectrically connected to a first end of the second conductivethrough-via and the second semiconductor device, such that the secondbuffer layer, the second conductive through-via, the secondsemiconductor device, the second molding material, and the secondredistribution line form a second package; forming a second conductiveball over and electrically connected to the second redistribution line;flipping the first package; after flipping the first package, forming anopening in the first buffer layer to expose a second end of the firstconductive through-via; flipping the second package; and after flippingthe second package, stacking the second package over the first packagesuch that the second conductive ball is over and electrically connectedto the second end of the first conductive through-via.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A package structure, comprising: a firstdielectric layer; a first semiconductor device over the first dielectriclayer; a first redistribution line in the first dielectric layer; asecond dielectric layer over the first semiconductor device; a secondsemiconductor device over the second dielectric layer; a secondredistribution line in the second dielectric layer; a conductivethrough-via over the first dielectric layer and electrically connectedto the first redistribution line; a conductive ball over the conductivethrough-via and electrically connected to the second redistributionline; and a molding material surrounding the first semiconductor device,the conductive through-via, and the conductive ball, wherein a top ofthe conductive ball is higher than a top of the molding material.
 2. Thepackage structure of claim 1, wherein a bottom of the conductive ball islower than the top of the molding material.
 3. The package structure ofclaim 1, wherein the molding material has a portion verticallyoverlapping the first semiconductor device.
 4. The package structure ofclaim 1, wherein the top of the molding material is higher than a top ofthe first semiconductor device.
 5. The package structure of claim 1,wherein the molding material has a portion between the firstsemiconductor device and the conductive ball.
 6. The package structureof claim 1, further comprising: a buffer layer between the seconddielectric layer and the molding material.
 7. The package structure ofclaim 6, wherein the top of the conductive ball is higher than a top ofthe buffer layer.
 8. The package structure of claim 6, wherein theconductive ball has a portion surrounded by the buffer layer.
 9. Thepackage structure of claim 6, wherein the buffer layer is in contactwith the molding material and the conductive ball.
 10. The packagestructure of claim 1, further comprising: a semiconductor package overthe second semiconductor device.
 11. A package structure, comprising: afirst dielectric layer; a first semiconductor device over the firstdielectric layer; a first redistribution line in the first dielectriclayer; a conductive through-via over the first dielectric layer andelectrically connected to the first redistribution line; a moldingmaterial surrounding the first semiconductor device and the conductivethrough-via; a conductive ball over the conductive through-via; a seconddielectric layer over the molding material; a second semiconductordevice over the second dielectric layer; a second redistribution line inthe second dielectric layer and electrically connected to the conductiveball; and a buffer layer in contact with the conductive ball and spacedapart from the second dielectric layer.
 12. The package structure ofclaim 11, wherein a bottom of the conductive ball is substantiallylaterally aligned with a top of the molding material.
 13. The packagestructure of claim 11, wherein a top of the conductive through-via issubstantially laterally aligned with a top of the molding material. 14.The package structure of claim 11, wherein a top of the conductive ballis higher than a top of the buffer layer.
 15. The package structure ofclaim 11, wherein the first semiconductor device is free from coverageby the molding material.
 16. A method, comprising: forming a firstconductive through-via over a first buffer layer; disposing a firstsemiconductor device over the first buffer layer; forming a firstmolding material to surround the first semiconductor device and thefirst conductive through-via; forming a first redistribution lineelectrically connected to a first end of the first conductivethrough-via and the first semiconductor device, such that the firstbuffer layer, the first conductive through-via, the first semiconductordevice, the first molding material, and the first redistribution lineform a first package; forming a first conductive ball over andelectrically connected to the first redistribution line; forming asecond conductive through-via over a second buffer layer; disposing asecond semiconductor device over the second buffer layer; forming asecond molding material to surround the second semiconductor device andthe second conductive through-via; forming a second redistribution lineelectrically connected to a first end of the second conductivethrough-via and the second semiconductor device, such that the secondbuffer layer, the second conductive through-via, the secondsemiconductor device, the second molding material, and the secondredistribution line form a second package; forming a second conductiveball over and electrically connected to the second redistribution line;flipping the first package; after flipping the first package, forming anopening in the first buffer layer to expose a second end of the firstconductive through-via; flipping the second package; and after flippingthe second package, stacking the second package over the first packagesuch that the second conductive ball is over and electrically connectedto the second end of the first conductive through-via.
 17. The method ofclaim 16, wherein stacking the second package over the first package isperformed such that a portion of the second conductive ball issurrounded by the first buffer layer.
 18. The method of claim 16,wherein stacking the second package over the first package is performedsuch that the second conductive ball has a portion protruding from a topof the first buffer layer.
 19. The method of claim 16, furthercomprising: bonding a semiconductor package to a second end of thesecond conductive through-via.
 20. The method of claim 16, furthercomprising: before forming the first redistribution line, thinning thefirst molding material to expose the first end of the first conductivethrough-via.